Soldier finds grid in part of book (9)
I believe the answer is:
paragraph
'book' is the definition.
(thesaurus)
'soldier finds grid in part' is the wordplay.
'soldier' becomes 'para' (short for paratrouper).
'finds' means one lot of letters go next to another.
'grid in part' becomes 'graph' (I am not sure about this - if you are sure you should believe this answer much more).
'para'+'graph'='PARAGRAPH'
'of' acts as a link.
Can you help me to learn more?
(Other definitions for paragraph that I've seen before include "short item" , "Chunk of text" , "Unit of text" , "Passage" , "Section, division of written piece" .)